1. Field of the Invention
The present invention relates to video systems for motion analysis and, in particular, to a video sampling motion analysis tool for real time motion analysis of repetitive or cyclic mechanical systems.
2. Statement of the Problem
Many manufacturing processes utilize mechanical equipment that undergoes cyclic or repetitive motion. When such high speed mechanical equipment does not operate properly or according to specification, the problem is often difficult to diagnose because the equipment is moving too fast. In addition to the movement of mechanical equipment, high speed repetitive motion may also occur in the movement of objects such as occurs with the movement of objects on a conveyor line. A need exists to provide a system that provides slow motion visual images of the high speed cyclic or repetitive objects while they are in operation to properly diagnose any mechanical problem or to view the repetitive motion of objects in general.
A number of commercial motion analyzers are available that aid in the diagnosis of such high speed equipment. In the article "High Speed Motion Analysis" by John J. Foley, Machine Design, March 10, 1988, Pages 117-121, a survey of current motion analysis techniques are set forth. One conventional approach to motion analysis is the use of video recording devices. These video systems utilize a recording camera, a strobe light to clearly capture the movement, and playback equipment which is used to playback the recorded high speed operation of the mechanical device at a much slower speed for diagnostic analysis. Such conventional high speed video approaches for motion analysis rely on taking a high speed recording of the entire mechanical operation and then using complex electronic circuitry to play the recording back at a much slower speed at a later time. One example of such conventional approaches is the Kodak EKtaPro 100 Motion Analyzer which captures up to 1000 full frames per second (up to 60000 pictures per minute) and provides instant replay with slow motion and stop action without blur. Another example is the UNILUX System 850 which can shoot video tape at speeds up to 600 frames per second. These conventional systems provide footage of the motion for later viewing. A need exists for a motion analyzer that permits real time evaluation of mechanical motion while the object is moving.
Such conventional motion analysis approaches generally require that the observed motion be sampled many times per cycle or event. Thus, these machines must have very fast sampling rates and they are not compatible with present video recorders.
Finally, such conventional motion recording systems are often expensive and utilize equipment that not only is bulky but difficult to set up and take down. The cameras and playback equipment to provide the slow motion playback are specially designed. As pointed out by Foley, above at page 119, such systems may cost between $60,000 to $120,000.
A need exists for a motion analysis tool which is not bulky, is easy to set up and take down, is less expensive, and which utilizes conventional video equipment. Furthermore, this equipment could be on line, capture images in real time, permit the user to view all or a portion of the repetitive cycle, and allow cycle-to-cycle comparison of the viewed portion.
3. Solution to the Problem
The motion analysis tool and method of the present invention is a real time video sampling machine that is capable of viewing all or any portion of repetitive or cyclic motion. By using a sampling technique (i.e., grabbing a video image of the motion in successive repetitions), the present invention simulates a complete or a portion of a cycle by taking one sample per cycle at various stages of the actual mechanical motion. This sampling technique allows a real time slow motion simulation of the mechanical operation to be viewed by the operator.
The analysis tool of the present invention operates in two basic modes. In the first mode of operation, the system is externally triggered by the operation of the mechanical device to be in synchronization with the motion of the mechanical device. A viewing window can then be established for either the full cycle of operation of the device or the window can be narrowed down to view only a desired portion of the cycle. The viewing window can be adjusted to be at any motion position within the cycle.
In the second mode of operation, the present invention is internally triggered and, therefore, operates asynchronously from the operation of the mechanical device. However, the user can adjust the frequency of the internal trigger to closely match the rate of the mechanical device. This allows the operator to freeze the sampling at any point in the machine cycle or to use the viewing window to view all or a selected portion of the cycle.
The user interface of the current implementation consists of a combined display and an operator interface. The operator interface is used by the operator to set up the analysis tool of the present invention and the display is used to view the slow motion images produced by the system.
The present invention utilizes a low cost CCD video camera (color or monochrome) and fiber optic strobe head mounted onto mechanical fixtures that can be attached to standard camera tripods or extensions. The compact system of the present invention can be easily packed into a case for airline travel and can be quickly set up or taken down at a desired location.
4. Search
A search was performed on the present invention and the results of the search uncovered the following patents:
______________________________________ Inventor Reg. No. Issued ______________________________________ Dietrich 3,275,744 9-27-66 Williams 3,390,229 6-25-68 Saiger 3,543,087 11-24-70 Dimmick 4,147,977 4-3-79 Karidis 4,487,075 12-11-84 Bixby 4,511,931 4-16-85 ______________________________________
Bixby discloses a conventional high speed video approach for motion analysis which relies on the slow motion playback of a recording. The Dietrich patent sets forth a vidicon camera in combination with a synchronized strobe scope for the analysis of spray coming from a nozzle. Saiger sets forth a lamp flashing circuit for a gas-filled flash tube which functions as a stroboscopic light source for viewing rapidly moving machinery. The Karidis patent makes use of a strobe light to illuminate injected gas bubbles in a liquid flow stream as a means for observing liquid flow conditions. Williams utilizes a strobe flash and camera for spray particle analysis. Finally, Dimmick utilizes a light source and oscilloscope to view rapidly moving objects over small relative distances such as the movements of relays.
None of the above references set forth either the structure or the method of the present invention pertaining to the progressive real time sampling of the motion as summarized in the next section.